This invention relates generally to systems for refrigerating food products and the like, and, more particularly, to refrigeration systems that maintain the product temperature within certain limits while using electrical power during only prescribed time periods of each day.
Electrical utilities are finding it increasingly difficult and expensive to meet the public's increased demands for electrical power. Changing lifestyles are causing this increased power demand to greatly outstrip increases in population. The difficulty in meeting the increasing demand for electrical power arises in part because of a concern for the effect additional and/or expanded power plants might have on air and water quality and on public safety.
The demand for electrical power varies widely with the time of day. Typically, summer afternoons and winter evenings are periods of particularly high usage. Conversely, night time periods between 12:00 midnight and 6:00 A.M. are periods of particularly low usage. During such periods of such low electrical power usage, much of the capacity of existing power plants is unused.
It is recognized that one viable alternative to the building of costly new power plants, or the expansion of existing plants, is to shift many uses of electrical power from periods of high usage to periods of low usage. For example, some commercial users of large amounts of electrical power scale back their operations at certain times of each day and shift those operations to time periods.
Electrical utilities have been implementing special rate schedules designed to encourage this time shifting of electrical power usage. Commercial users of electrical power must pay substantially more for each unit of power during periods of high power usage than during periods of low power usage. In fact, the cost ratio for these two periods can be as high as about ten.
One substantial use of electrical power is in the refrigeration of food, particularly by grocery stores. Enormous amounts of electrical power are consumed in maintaining certain food products either frozen or colder than room temperature, 24 hours of each day. Because of this requirement to continuously maintain the temperature of food products at prescribed cold temperatures, it has not generally been thought to be feasible for businesses of this kind to use the time-shifting technique described above to reduce their cost of electrical power.
It should, therefore, be appreciated that there is a need for a refrigeration system for refrigerating products such as food that maintains the temperature of the product within certain limits while using electrical power substantially only during certain predetermined periods of each day; when electrical power is relatively inexpensive. The present invention fulfills this need.